The Bearings Expert

GETTING THE "DIRT" ON DOWNTIME

Wed, 07 Sep 2022 11:54:05 GMT

You know that dreaded sound an alarm goes off to announce one of the units has gone down and ‘literally’ grinds to a halt. You know you are instantly into losing money and time, with customers relying on you. In these times of escalating costs, this is the last thing you need.

Article by David Riley, Consultant Engineer JAD Associates

So often this problem is a bearing. A recent study by the National Research Council of Canada found that 82% of bearing wear is caused by particle contamination and that this makes lubrication contamination the leading cause of premature failures.

BEARING FAILURE: A PROBLEM FOR THE WORLD OF MANUFACTURING

In a recent publication “Beyond the Essentials, Lubrication Best Practices: It’s Not the Destination… It’s the Journey” , by Paul Llewellyn, the problem of particle contamination in bearing lubricant is discussed, as a common problem encountered by bearing users around the world.

Lubrication contamination occurs regardless of industry, geographic location, facility size, standard operating procedures, and the training and experience of the maintenance staff. And this is because there isn’t always that much that can be done to completely avoid lubrication contamination. All it takes is one particle of dust, dirt, or other debris to get entangled within your bearing lubricant, for its effects to deteriorate the asset’s reliability. This makes the margin of error for preventing lubrication contamination very small. However, there are steps that can be put in place to minimise the disastrous effects of bearing lubrication contamination.

HERE'S THE "DIRT"

The definition of contamination: The presence of a constituent, impurity, or some other undesirable element that spoils, corrupts, infects, or makes unfit, a material, physical body, natural environment, workplace, etc.

In the case of bearing lubrication, these contaminants vary depending on industry. But they can mean dirt, dust, saw dust, metal shavings, chemicals, moisture, and even mixed grease types. When your lubricant becomes contaminated, it is no longer suitable for its purpose, and it needs to be taken out of service to prevent severe damage to the asset and production is forced to shut down.

" Don’t just say ‘faulty bearing’ - the problem will often be more than that. "

David Riley, Consultant Engineer, JAD Analysis

LUBRICATION CONTAMINATION - DEFEATS YOUR MAINTENANCE SCHEDULES

Lubrication contamination can reduce the amount of time an asset is able to operate without maintenance from years to months… and in some cases weeks or days.
Lubrication contamination can cause machinery bearings to seize up as the grease thickens and eventually hardens.
Lubrication c ontamination can scratch, wear and shave off pieces on metal bearings leading to faster and more unpredictable failures.

NOT ALWAYS A "FAULTY" BEARING

How can you tell if a bearing is affected by contamination? Condition monitoring is often used to identify abnormal vibration, but many pieces of equipment do not have the benefit of such monitoring. Contamination in the lubricant can be identified by visual inspection of load bearing surfaces once a bearing has been removed from service. Often a machine failure will be attributed to a “Faulty Bearing” when in fact contamination in the lubricant, possibly caused by a damaged seal or a dirty grease gun, for example, is the root cause of the damage.

ESTABLISH THE REAL PROBLEM

To attain the maximum lubrication effectiveness, it is essential that bearing failures are correctly investigated to establish a true root cause and prevent unnecessary recurrence. Visual inspection of the bearing’s internal surfaces by a professional engineer such as JAD Analysis in Lincolnshire, along with, where possible, a chemical analysis of the lubricant to identify contaminant particles will satisfy this requirement.

Understanding failures will often result in less unplanned failures and the costly downtime they cause, a reduction in the amount of grease consumed, and less bearing purchases. In these times of increasing economic pressure on businesses, understanding these failures is an overhead not to be missed.

TALK TO US ABOUT YOUR BEARING ISSUES

Looking for expert help in understanding why your bearing failed and preventing problems in the future? JAD Analysis is independent from any one bearing manufacturer, so you can trust our experts to provide unbiased reports without prejudice. If you're interested in finding out what caused a bearing to fail or become damaged and possibly using our services, please call us on +44 (0)1673 843059 or use the contact form on this page to email your questions. You can upload a photograph of the bearing too either to gain a simple low cost rapid response or to help us quote for a more in depth piece of work.

ADDING TOO MUCH GREASE MAKES BEARING FAILURES MORE LIKELY

Wed, 10 Aug 2022 11:54:05 GMT

Yes, regrettably, that is often the case. Many maintenance departments add grease to their rotating equipment on a regular basis and believe they are acting in the best interests of their machines. But grease is not a cure-all, at least without a little added ‘science.

Article by David Riley, Consultant Engineer JAD Associates

I recently spoke to the manager of an electrical motor repair and rewind company who recognised that adding too much grease often had unexpected side effects. He commented: ‘Many of the motors I rebuild proved end users did not always understand this fact’. He told me of a factory manager who suspected the bearings in one of his electric motors was starting to overheat. To overcome the problem, he added more grease to the housing until no more would go in. For about 10 minutes the temperature dropped but then the temperature started increasing again until the motor tripped. Faulty bearings were blamed, and the motor was sent for a rebuild.

AN EXTRA PUMP "FOR LUCK"

An investigation of the problem was undertaken by JAD Associates; this highlighted a motor manufacturer’s recommended grease interval of a few thousand hours running before a defined quantity of new grease should be added. The reality was that the motor was greased on a weekly basis using a grease gun that suppled the specified amount of new grease in just two strokes of the pump.

" When the maintenance technician was observed, he added three times the required quantity and often added an extra pump ‘for luck’. When it was explained that too much grease was causing the problems this was met with some scepticism. "

When the maintenance technician was observed, he added three times the required quantity and often added an extra pump ‘for luck’. When it was explained that too much grease was causing the problems this was met with some scepticism.

YOU WILL END UP 'CHURNING'

Firstly “why does adding grease cause the bearing housing to cool then?” was asked. The reply was that the new grease had been taken from a cold storeroom and this cooler grease lowered the bulk temperature of the remaining lubricant until once again the grease got hot and tripped the motor.

When the motor was stripped, the bearing housings, and the void between the inner and outer raceways, was found to be completely full of compacted and hard grease. JAD was then able to explain that this excessive grease fill had not allowed cooling air to flow around the housing. This resulted in the grease in the housing getting hot due to an effect often referred to as ‘churning’ with no way for any heat generated to dissipate.

JUST HAVE A PADDLE

I was asked why, if the bearings were not faulty, was the motor drawing more power than usual and getting hot?

I explained the effect: When you are on a beach and feel like a walk, its often good to step into the water and just ‘have a paddle’. When, however, you try to walk up to your waist in the sea the effort needed is much greater and even in cold water you start to feel hotter and begin to use much more energy. This is what happens with the grease. The mechanical effort needed to rotate a fully packed bearing is greater than that required with a correctly packed and normal item. This mechanical effort generates heat, causing overheating and results in the grease degrading. The lubricant starts getting stiffer. That stiffness, in turn, causes more effort to be needed and eventually the system stops rotating.

MOST "SEALED FOR LIFE" BEARINGS CONTAIN A GREASE FILL OF BETWEEN 25% TO 35%

The message is clear, confirm the manufacturer’s recommendation for re-lubricating and stick to it! Understand how much grease you are delivering and never add one more pump for ‘luck‘- your luck may just run out and cost a fortune to repair.

TALK TO US ABOUT YOUR BEARINGS ISSUES

INCREASES IN THE GLOBAL PRICE OF BEARINGS – REDUCING THE IMPACT

Thu, 23 Jun 2022 11:54:05 GMT

Rolling Element Bearings of all types and sizes are, like many other Engineering components, rapidly increasing in price due to the current global economic circumstances.

Article by David Riley, Consultant Engineer JAD Associates

In the first quarter of this year (2022) many large manufacturers had already increased prices by an average of 8%, it has been reported. The Russian-Ukrainian war also continues to affect the prices of raw materials and related components used in bearing manufacture. Available statistics are showing some critical raw materials increasing by over 100%, month on month. Natural Gas and electricity costs have also adversely affected bearing makers’ overheads, forcing prices up. As all makers are similarly affected, the cost of new bearings can only be heading one way, which is bad news for all bearing users.

Extending bearing life, incorporating maintenance, and reducing costs

Previously, many end users would treat all sizes of rolling element bearings as disposable items and simply change them in a failed machine, without thought. Economic considerations must surely start to change this way of thinking, with far more focus on route cause analysis to extend bearing life and make maintenance more cost effective. Throwing away an old and used bearing without checking its condition can often rob a machine user of valuable information on why bearing replacement was needed, and the also the condition of other machine parts.

" A recent investigation undertaken by ourselves highlighted that each time a set of bearings was changed, the accuracy of the shaft and housing was also affected "

Recently, we at JAD Analysis witnessed an end-user change bearings at increasingly regular intervals than was expected. The instinct was to blame the batch of bearings. Bearings from reputable manufacturers are extremely high precision items and have quality control checks in place all through the production process. Manufacturing defects in a batch of bearings is therefore highly unusual. A recent investigation undertaken by JAD highlighted that each time a set of bearings was changed, the accuracy of the shaft and housing was also affected. Metal was broached away from the shaft journals and housings, where interference fits were originally intended because of the removal process. In cleaning the journals and housings after bearing removal with an abrasive cloth or similar the size and shape of the shaft can be further affected. Marks on the outer surfaces of the bearing rings and on the load bearing contact marks will often show that this loss of fitting accuracy has occurred.

Many of the bearing failures we see can be avoided, thus reducing expenditure on new expensive parts but also eliminating the cost of process down time that can be crippling for an already stretched manufacturer.

Investigate your failed bearing to reduce costs in the future

Having a removed bearing inspected by an expert such as JAD Analysis (based in England, UK) who look for tell tail signs of impending problems, is one method forward-thinking organisations are employing to improve profitability and reduce costs. The cost of an 50mm bore bearing analysis, for example, is often less than the price of a full new set of replacement bearings.

Talk to us about your bearing issues